An operating mechanism for an hydraulic cylinder

Abstract

 The operating mechanism comprises a pedal (1) and a link (6) connected at one end to an hydraulic piston (8) and cylinder (7) and at the other end to the pedal (1) by means of a shaft (10) which extends from the end of the link (6) through an aperture (4) in the pedal by an amount (a) equal to or greater than the distance (b) through which the aperture (4) travels. Movement is transferred from the pedal (1) to the lever (6) by means of abutting surfaces (5a, 5b).
The slidable coupling provided by the shaft (10) and aperture (4) retains abutting surfaces (5a, 6) in alignment even when separated by distances upto or greater than the travel of the lever.

Description

[0001] This invention relates to operating mechanisms for devices such as hydraulic cylinders in particular to operating mechanisms for motor vehicle brake master cylinders.

[0002] Conventional motor vehicle brake master cylinders are operated by a pedal lever mounted for pivotal movement by an operator between a rest position and an engaged position. The pedal is connected to the hydraulic cylinder by a link which is reciprocable in the plane of movement of the lever. The connection between the link and the lever usually comprises a clevis on the lever which is connected to a tongue or clevis on the link by means of a pivot pin which lies transversely to the plane of movement of the lever, the pin being held in place by a split pin.

[0003] Although this construction is unusally fully effective, errors in assembly or failure of the components of the connection can lead to the lever and link becoming detached from each other. The occurence of such an event during the use of a vehicle could endanger the safety of the occupants of the vehicle.

[0004] According to the present invention there is provided an operating mechanism for an hydraulic cylinder comprising a lever adapted to be mounted for pivotal movement by an operator between a rest position and an engaged position, and a link adapted for connection at one end to a piston in the hydraulic cylinder and connected at the other end to the lever for reciprocation by the lever in the plane of movement of the lever, characterised in that the connection between the link and the lever comprises an abutment on the lever which engages an abutment on the link when the lever moves in a direction from the rest position towards the engaged position, and a slidable coupling for retaining the abutments in alignment when separated from each other by an amount equal to or greater than the distance through which the abutment on the lever travels when the lever is moved between the rest and engaged positions.

[0005] By avoiding the use of the pivot pins in the connection between the lever and the link the risk of failure of the operating mechanism is reduced. Moreover, since the sliding connection is capable of maintaining the abutments in alignment even when separated by an amount greater than the travel of the lever., the link cannot become detached from the lever.

[0006] Preferably the slidable coupling between the link and lever comprises a shaft on one, and an aperture in the other through which the shaft projects. The shaft desirably forms part of the link and in the preferred embodiment of the invention comprises a projection extending towards the lever and through an aperture in the lever so that when the abutments are in engagement the pin projection extends into the mouth of the aperture by an amount equal to or greater than the distance through which the aperture travels when the lever is moved between the rest and engaged positions.

[0007] Usually the lever will be biased against movement towards the engaged position.

[0008] If desired, the shaft may carry a further abutment for example in the form of a circlip, which is engaged by the lever when the lever is returned to the` rest position thus ensuring that the link always follows closely the movement of the lever even when the lever is suddently moved into its rest position.

[0009] The link will preferably be biased towards the rest position of the lever so that the abutments on the lever and link are in engagement during travel of the lever from the engaged position towards the rest postion. In order to ensure that the abutments on the lever and link are in engagement even in the rest position of the lever, the mechanism preferably includes a stop with which the lever engages in the rest position, and which biases the lever towards the engaged position. Where the operating mechanism of the invention is used for the control of a motor vehicle brake master cylinder, the stop is preferably in the form of a brake warning light switch.

[0010] The invention specifically provides an hydraulic cylinder assembly comprising an hydraulic cylinder, a piston reciprocable within the said cylinder between a first and second position and being biased towards the first position, and an operating linkage according to the invention in which the link is connected at the said one end to the piston to move the piston out of the first position when the lever is moved towards the engaged position.

[0011] A preferred embodiment of the invention will now be described, by way of example only, with reference to the drawings, in which:-

Figure 1 is a schematic side view of an embodiment of the operating mechanism of the invention; and

Figure 2 is a partial end view of the mechanism of Figure ₁ taken along the line II-II.

[0012] The operating mechanism illustrated in the drawings is designed specifically for a motor vehicle brake master cylinder. The invention can however be used in other applications, for example for operating other types of hydraulic cylinders in motor vehicles or elsewhere.

[0013] Referring to the drawings, the operating mechanism comprises a lever 1 in the form of a pedal mounted at its upper end for pivotal movement about a transverse pivot pin 2 between a rest position illustrated in full lines and an engaged position, illustrated in broken lines. The pedal 1 is biased against movement towards the engaged position by means of a coil spring (not shown) o-L conventional construction acting about the pivot pin 2.

[0014] A flange 3 formed is on the rear edge of the pedal 1 and, as best seen in Figure 2, is provided with an elongated aperture 4. The flange 3 is shaped to form a recess, the forwardly facing surface 5a of which acts as an abutment surface and engages with a complementarily shaped abutment 5b on a link 6 which interconnects the pedal 1 with the piston of an hydraulic brake master cylinder indicated schematically at 7, of conventional construction. This cylinder includes a piston 8 which is connected directly to the link 6 reciprocable within the cylinder between a first position, corresponding to the rest position of the pedal 1, and a second position, corresponding to the engaged position of the pedal ₁, and a second position, corresponding to the engaged position of the pedal 1. A spring 9 within the cylinder biases the piston into the first position.

[0015] The link 6 is in the form of a rod and the surface 5 is formed by a bush of plastics material, e.g. nylon. A shaft 10 in the form of a smooth pin extends from the end of the link 6 in a direction away form the engaged position of the pedal 1 and passes through the aperture 4. A spring circlip 11 is mounted in a circumferential groove on the shaft ₁0 adjacent the rearwardly facing wall of the flange 3. The shaft 10 extends into the aperture 6 by an amount a which is at least equal to the distance b through which the aperture 6 travels when the pedal 1 is moved between the rest and engaged positions.

[0016] A brake warning light switch 12 having a spring loaded contact 14 is mounted adjacent the upper end of the pedal 1 for operation by the pedal when the pedal is in the rest position.

[0017] In use, movement of the pedal towards the engaged position against the bias of the coil spring about the pivot pin 2 is transferred to the link 6 by virtue of the engagement between the abutment surfaces 5a and 5b on the flange 3 and the bush carried by the link 6, the link is therefore reciprocated in the plane of movement of the pedal 1 and causes the piston 8 to reciprocate in the cylinder 7 thus pressurising The elongation of the aperture 4 accommodates the relative movement of the shaft 10 and the pedal 1 during the travel of the pedal ₁.

[0018] When the pedal 1 is released, the pedal returns to its rest position under the influence of the coil spring, allowing the piston 8 and the link 6 to move towards the rest position of the pedal 1 under the influence of the spring 9. Throughout this movement the abutment surfaces 5a and 5b will be held in engagement with each other. If the pedal 1 is suddenly released, for example in the event of the operator's foot slipping from the brake, the rearwardly facing wall of the flange 3 will engage with the circlip 11 thus ensuring that the link 6 always follows the movement of the pedal 1.

[0019] If the circlip 11 should have been inadvertently omitted during assembly, or is accidentally removed from the shaft ₁0, the link 6 cannot become disengaged from the pedal 1 because the projection 10 extends beyond the rear surface of the flange 3 by an amount greater than the maximum travel of the aperture 4*

[0020] The warning light switch 12 acts as a stop for the pedal 1 as it returns to the rest position, and the small bias exerted on the pedal by the contact ₁₄ ensures that the abutment surfaces 5a and 5b are in engagement when the pedal 1 is in the rest position.

Claims

1. An operating mechanism for an hydraulic cylinder comprising a lever adapted to be mounted for pivotal movement by an operator between a rest position and an engaged position, and a link adapted for connection at one end to a piston in the hydraulic cylinder and connected at the other end to the lever for reciprocation by the lever in the plane of movement of the lever, characterised in that the connection between the link and the lever comprises an abutment on the lever which engages an abutment on the link when the lever moves in a direction from the rest position towards the engaged position, and a sliding coupling for retaining the abutments in alignment when separated from each other by an amount equal to or greater than the distance through which the abutment on the lever travels when the lever is moved between the rest and engaged positions.

2. A mechanism according to claim 1 wherein the sliding coupling between the link and the lever comprises a shaft on one and an aperture in the other through which the shaft projects.

3. A mechanism according to claim 2 wherein the shaft projects from the link towards the lever and through an aperture in the lever such that, when the abutments are in engagement, the shaft extends into the mouth of the aperture by an amount equal to or greater than the distance through which the aperture travels when the lever is moved between the rest and engaged positions.

4. A mechanism according to claim 3 wherein the shaft carries a further abutment engagable with the lever when the lever is returning to the rest position.

5. A mechanism according to claim 4 wherein the further abutment comprises a circlip around the shaft.

6. A mechanism according to any one of claims 1 to 5 wherein the lever is biased against movement towards the engaged position.

7. A mechanism according to any one of claims 1 to 6 wherein the lever engages a stop in the rest position which biases the lever towards the engaged popiti,)n.

8. A mechanism according to any one of claims 1 to 7 wherein the link is biased towards the rest position of the lever.

9. An hydraulic cylinder assembly comprising an hydraulic cylinder, a piston reciprocable within the said cylinder between a first and second position and being biased towards the first position, and an operating linkage according to any one of claims ₁ to 7 in which the link is connected at the said one end to the piston to move the piston out of the first position when the lever is moved towards the engaged position.

10. An assembly according to claim 9 wherein the hydraulic cylinder is a motor vehicle brake master cylinder and the lever is a brake pedal.

Drawing